Fractures of the thoracolumbar region of the spine are serious disabling injuries resulting in personal suffering and significant loss to society. These result from many causes, such as high speed auto accidents, falls, blows, sports and ejection of airplane pilots at high speed. There is high risk associated with these injuries because of certain anatomic relationships. The junction of the conus medularis and cauda equina is adjacent to the thoracolumbar junction, the most common site of spinal injury. Further, this junction between the relatively rigid rib cage and the more flexible lumbar spine creates a potential for second injury during the time of transport to and treatment in the hospital. The treatment of these injuries depends to a large degree on the determination of the stability/instability status of the spine. Although there are several clinical guidelines, the decision is often based on subjective judgement. There are no objective experimental studies to help the physician make this important decision. The primary goal of our proposal is to develop such objective guidelines by producing clinically relevant spinal injuries, objectively evaluating their spinal instability, and then correlating one with the other. Fractures and dislocations will be produced dynamically in fresh thoracolumbar spine specimens to simulate clinical situations. Loads, displacements and deformations will be recorded during trauma, using computers and high speed movie cameras. X-rays and CT-scans before and after trauma will be taken. Multi-directional instability will be measured before and after trauma. The injured specimen will be studied morphologically, and its image will be reconstructed using computer graphics for three-dimensional visualization of the fractures. The data will be analyzed to determine relationships between various types of parameters, but especially between the roentgenographic images (x-rays and CT-scans) and the multi-directional spinal instability of the injured specimens. Clinical relevance is one of the primary aims of this study and it may participate in health care cost containment at the level of diagnosis and treatment.